Apparatus and method for reducing energy consumption by cellular base stations

ABSTRACT

A method for reducing energy consumption of a base station is described. A first pilot channel is transmitted via a first antenna using a first downlink power amplifier. A second pilot channel is transmitted via a second antenna using a second downlink power amplifier. It is determined that no multiple-input and multiple-output users are in a cell corresponding to the base station. The second pilot channel is shut off.

CLAIM OF PRIORITY

The present application for patent is a Divisional and claims priorityto patent application Ser. No. 12/985,732 entitled “APPARATUS AND METHODFOR REDUCING ENERGY CONSUMPTION BY CELLULAR BASE STATIONS” filed Jan. 6,2011, now allowed, which claims priority from U.S. Provisional PatentApplication Ser. No. 61/294,047, filed Jan. 11, 2010, for “ENERGYSAVINGS IN CELLULAR BASE STATIONS,” all of which are incorporated byreference herein.

TECHNICAL FIELD

The present disclosure relates generally to wireless communicationsystems. More specifically, the present disclosure relates to systemsand methods for energy savings in cellular base stations.

BACKGROUND

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, video, data, and so on.These systems may be multiple-access systems capable of supportingsimultaneous communication of multiple terminals with one or more basestations.

As precious natural resources are consumed, it has become beneficial toreduce the power consumption of computing devices. One such device wherepower consumption may be reduced is a base station.

Base stations are always on and always consuming power. Oftentimesportions of base stations are on when no wireless communication devicesare near the base station or utilizing the services of the base station.Benefits may be realized by reducing the energy consumption of basestations.

SUMMARY

A method for reducing energy consumption of a base station is described.A first pilot channel is transmitted via a first antenna using a firstdownlink power amplifier. A second pilot channel is transmitted via asecond antenna using a second downlink power amplifier. It is determinedthat no multiple-input and multiple-output users are in a cellcorresponding to the base station. The second pilot channel is shut off.

Shutting off the second pilot channel may include shutting off thesecond downlink power amplifier. The base station may be a Node B. Themethod may be performed by a radio network controller via instructionssent to the base station. The first pilot channel and the second pilotchannel may be used for multiple-input and multiple-output transmissionsto a user equipment.

A method for reducing energy consumption of a base station is alsodescribed. The method includes communicating with one or more userequipments using n carriers. The method also includes determining that aload of one or more of the n carriers is below a carrier load threshold.One or more user equipments are redirected from the one or more carrierswith loads below the carrier load threshold to one or more othercarriers. The one or more carriers with loads below the carrier loadthreshold are turned off.

Turning off the one or more carriers with loads below the carrier loadthreshold may include turning off physical equipment corresponding tothe one or more carriers with loads below the carrier load threshold.Physical equipment may include a downlink power amplifier. Physicalequipment may also include at least one of channel cards, digital signalprocessors, field programmable gate arrays, application-specificintegrated circuits, clocks and backhaul interface units on a basebandunit. The method may include communicating with the one or more userequipments using the one or more carriers with loads above the carrierload threshold.

Redirecting the one or more user equipments from the one or morecarriers with loads below the carrier load threshold to the one or morecarriers with loads above the carrier load threshold may includeinstructing the one or more user equipments to switch to a differentmodulation and coding scheme or to switch to a different frequency.

It may be determined whether a total load of the one or more carrierswith loads above the carrier load threshold is above a combined carrierload threshold. If the total load of the one or more carriers with loadsabove the carrier load threshold is above the combined load threshold, apreviously-switched-off carrier may be turned on and one or more userequipments may be redirected from the one or more carriers with loadsabove the carrier load threshold to the previously-turned-off carrier.Turning on the previously-switched-off carrier may include turning onphysical equipment corresponding to the previously-switched-off carrier.

The method may be performed by the base station. The base station may bea Node B. The method may also be performed by a radio network controller(RNC) via instructions sent to the base station.

A method for reducing energy consumption of a base station is alsodescribed. The method includes communicating with one or more userequipments using one or more carriers. It is determined that a load ofany of the one or more carriers is below a carrier load threshold. Oneor more baseband unit subunits to disable on the one or more carriersare determined. The one or more of the baseband unit subunits aredisabled. The method further includes communicating with the one or moreuser equipments using the one or more carriers and only the basebandunit subunits that have not been disabled.

The method may further include determining that a load of any of the oneor more carriers is above the carrier load threshold. One or morebaseband unit subunits that have been disabled may be re-enabled. Thebaseband unit subunits may include channel cards, digital signalprocessors, field programmable gate arrays, application-specificintegrated circuits, clocks and backhaul interface units. The basestation may be a Node B. The method may be performed by a radio networkcontroller (RNC) via instructions sent to the base station.

A wireless device configured for reducing energy consumption isdescribed. The wireless device includes a processor, memory inelectronic communication with the processor and instructions stored inthe memory. The instructions are executable by the processor to transmita first pilot channel via a first antenna using a first downlink poweramplifier. The instructions are also executable by the processor totransmit a second pilot channel via a second antenna using a seconddownlink power amplifier. The instructions are further executable by theprocessor to determine that no multiple-input and multiple-output usersare in a cell corresponding to the wireless device. The instructions arefurther executable by the processor to shut off the second pilotchannel.

A wireless device configured for reducing energy consumption is alsodescribed. The wireless device includes a processor, memory inelectronic communication with the processor and instructions stored inthe memory. The instructions are executable by the processor tocommunicate with one or more user equipments using n carriers. Theinstructions are also executable by the processor to determine that aload of one or more of the n carriers is below a carrier load threshold.The instructions are further executable by the processor to redirect oneor more user equipments from the one or more carriers with loads belowthe carrier load threshold to one or more other carriers. Theinstructions are also executable by the processor to turn off the one ormore carriers with loads below the carrier load threshold.

A wireless device configured for reducing energy consumption is furtherdescribed. The wireless device includes a processor, memory inelectronic communication with the processor and instructions stored inthe memory. The instructions are executable by the processor tocommunicate with one or more user equipments using one or more carriers.The instructions are also executable by the processor to determine thata load of any of the one or more carriers is below a carrier loadthreshold. The instructions are further executable by the processor todetermine one or more baseband unit subunits to disable on the one ormore carriers. The instructions are also executable by the processor todisable the one or more baseband unit subunits. The instructions arefurther executable by the processor to communicate with the one or moreuser equipments using the one or more carriers and only the basebandunit subunits that have not been disabled.

A wireless device configured for reducing energy consumption isdescribed. The wireless device includes means for transmitting a firstpilot channel via a first antenna using a first downlink poweramplifier. The wireless device also includes means for transmitting asecond pilot channel via a second antenna using a second downlink poweramplifier. The wireless device further includes means for determiningthat no multiple-input and multiple-output users are in a cellcorresponding to the wireless device. The wireless device also includesmeans for shutting off the second pilot channel.

A computer-program product for reducing energy consumption of a basestation is described. The computer-program product includes anon-transitory computer-readable medium having instructions thereon. Theinstructions include code for causing a base station to transmit a firstpilot channel via a first antenna using a first downlink poweramplifier. The instructions also include code for causing the basestation to transmit a second pilot channel via a second antenna using asecond downlink power amplifier. The instructions further include codefor causing the base station to determine that no multiple-input andmultiple-output users are in a cell corresponding to the base station.The instructions also include code for causing the base station to shutoff the second pilot channel.

A wireless device configured for reducing energy consumption is alsodescribed. The wireless device includes means for communicating with oneor more user equipments using n carriers. The wireless device alsoincludes means for determining that a load of one or more of the ncarriers is below a carrier load threshold. The wireless device furtherincludes means for redirecting one or more user equipments from the oneor more carriers with loads below the carrier load threshold to one ormore other carriers. The wireless device also includes means for turningoff the one or more carriers with loads below the carrier loadthreshold.

A wireless device configured for reducing energy consumption is furtherdescribed. The wireless device includes means for communicating with oneor more user equipments using one or more carriers. The wireless devicealso includes means for determining that a load of any of the one ormore carriers is below a carrier load threshold. The wireless devicefurther includes means for determining one or more baseband unitsubunits to disable on the one or more carriers. The wireless devicealso includes means for disabling the one or more baseband unitsubunits. The wireless device further includes means for communicatingwith the one or more user equipments using the one or more carriers andonly the baseband unit subunits that have not been disabled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system with multiple wirelessdevices;

FIG. 2 is a block diagram illustrating selected components of a wirelesscommunication system;

FIG. 3 is a block diagram illustrating a Node B and a radio networkcontroller (RNC) interface with a packet network interface;

FIG. 4 is a block diagram of a Node B for use in the present systems andmethods;

FIG. 5 is a block diagram of a Node B with multiple radio equipments(RE) that are separated from the radio equipment control (REC);

FIG. 6 is a flow diagram of a method for reducing power consumption of aNode B by switching off multiple-input and multiple-output (MIMO)transmissions;

FIG. 7 is a flow diagram of a method for reducing power consumption of aNode B by shutting off one or more carriers;

FIG. 8 is a flow diagram of a method for disabling baseband unit (BBU)subunits to reduce energy consumption on a Node B;

FIG. 9 is a block diagram of a transmitter structure and/or processimplemented in a Node B;

FIG. 10 illustrates certain components that may be included within aNode B; and

FIG. 11 illustrates certain components that may be included within aradio network controller (RNC).

DETAILED DESCRIPTION

The 3^(rd) Generation Partnership Project (3GPP) is a collaborationbetween groups of telecommunications associations that aims to define aglobally applicable 3^(rd) generation (3G) mobile phone specification.The 3GPP may define specifications for the next generation of mobilenetworks, mobile systems and mobile devices. In 3GPP, a mobile stationor device may be referred to as a “user equipment” (UE).

FIG. 1 shows a wireless communication system 100 with multiple wirelessdevices. Wireless communication systems 100 are widely deployed toprovide various types of communication content such as voice, data, andso on. A wireless device may be a Node B 104 a-d or a user equipment(UE) 116.

The wireless communication system 100 may include a radio access network(RAN) 118 operating according to Universal Mobile TelecommunicationsSystem (UMTS). A radio access network (RAN) 118 may include one or moreradio network subsystems (RNS) 108 a-b. Each radio network subsystem(RNS) 108 may include one or more Node Bs 104 and one or more radionetwork controllers (RNCs) 106 a-b. A radio access network (RAN) 118 mayalso be referred to as a “radio network” or an “access network.” Theradio access network (RAN) 118 may be a UMTS Terrestrial Radio AccessNetwork (UTRAN). A UMTS Terrestrial Radio Access Network (UTRAN) is acollective term for the Node Bs 104 and the control equipment for theNode Bs 104 (or radio network controllers (RNCs) 106 a-b) it containswhich make up the UMTS radio access network (RAN) 118. This is a thirdgeneration (3G) communications network which can carry both real-timecircuit-switched and internet protocol (IP) based packet switchedtraffic types. The UTRAN provides an air interface access method for theuser equipment (UE) 116. Connectivity is provided between the userequipment (UE) 116 and a core network 102 by the UTRAN. The radio accessnetwork (RAN) 118 may transport data packets between multiple userequipments (UEs) 116.

The UTRAN may be connected internally or externally using fourinterfaces: the Iu interface 110 a-b, the Uu interface 101, the Iubinterface 114 a-d and the Iur interface 112. The UTRAN may be attachedto a Global System for Mobile Communications (GSM) core network 102 viaan external interface referred to as the Iu interface 110. One or moreradio network controllers (RNCs) 106 may support the Iu interface 110.In addition, a radio network controller (RNC) 106 may manage a set ofbase stations called Node Bs 104 through the Iub interfaces 114. The Iurinterface 112 may connect two radio network controllers (RNCs) 106 witheach other. The UTRAN is largely autonomous from the core network 102since the radio network controllers (RNCs) 106 are interconnected by theIur interface 112. The Uu interface 101 also connects the Node B 104with a user equipment (UE) 116, while the Iub interface 114 is aninternal interface that connects the radio network controller (RNC) 106with the Node B 104.

The radio access network (RAN) 118 may be further connected toadditional networks outside the radio access network (RAN) 118, such asa corporate intranet, the Internet or a conventional public switchedtelephone network (PSTN) and may transport data packets between eachuser equipment (UE) 116 and the outside networks.

FIG. 2 is a block diagram illustrating selected components of a wirelesscommunication system 200. The wireless communication system 200 mayinclude radio network controllers (RNCs) 206 a-d coupled to Node Bs 204a-c (also referred to as base stations or wireless base transceiverstations) via Iub interfaces 214 a-c. The Node Bs 204 may communicatewith user equipments (UEs) 216 a-e through corresponding wirelessconnections. A user equipment (UE) 216 may also be referred to as aremote station, a mobile station or a subscriber station.

A communications channel may include a downlink for transmissions from aNode B 204 to a user equipment (UE) 216, and an uplink for transmissionsfrom a user equipment (UE) 216 to a Node B 204. A radio networkcontroller (RNC) 206 may provide control functionalities for one or moreNode Bs 204. Each radio network controller (RNC) 206 may be coupled to apublic switched telephone network (PSTN) 220 through a mobile switchingcenter (MSC) 222 a-b.

In one configuration, a radio network controller (RNC) 206 may becoupled to a packet switched network (PSN) (not shown) through a packetdata server node (PDSN) (not shown). Data interchange between variousnetwork elements, such as a radio network controller (RNC) 206 and apacket data server node, can be implemented using any number ofprotocols, for example, the Internet Protocol (IP), an asynchronoustransfer mode (ATM) protocol, T1, E1, frame relay and other protocols.

A radio network controller (RNC) 206 may fill multiple roles. Forexample, the radio network controller (RNC) 206 may control theadmission of new mobiles or services attempting to use a Node B 204. Theradio network controller (RNC) 206 may also control a Node B 204.Controlling admission ensures that user equipments (UEs) 216 areallocated radio resources (bandwidth and signal/noise ratio) up to whatthe network has available. It is where the Iub interface 214 terminates.A radio network controller (RNC) 206 may act as a serving radio networkcontroller (RNC) 206 that terminates the user equipment's (UE's) 216link layer communications. The serving radio network controller (RNC)206 may also control the admission of new user equipments (UEs) orservices attempting to use the core network 102 over the Iu interface110.

In a multiple-input and multiple-output (MIMO) system, there are N (# oftransmitter antennas) by M (# of receiver antennas) signal paths fromthe transmit and the receive antennas, and the signals on these pathsare not identical. A multiple-input and multiple-output (MIMO) systemcreates multiple data transmission pipes. The pipes are orthogonal inthe space-time domain. The number of pipes equals the rank of thesystem. Since these pipes are orthogonal in the space-time domain, theycreate little interference with each other. The data pipes are realizedwith proper digital signal processing by properly combining signals onthe N×M paths. A transmission pipe may not correspond to an antennatransmission chain or any one particular transmission path.

Communication systems may use a single carrier frequency or multiplecarrier frequencies. Each communication link between a user equipment(UE) 216 and a Node B 204 a may incorporate a different number ofcarrier frequencies. A user equipment (UE) 216 may be any data devicethat communicates through a wireless channel. A user equipment (UE) 216may be any of a number of types of devices including but not limited toa PC card, a compact flash, an external or internal modem, or a wirelessphone. A user equipment (UE) 216 may be mobile or stationary.

A user equipment (UE) 216 that has established an active traffic channelconnection with one or more Node Bs 204 is referred to as an active userequipment (UE) 216, and is said to be in a traffic state. A userequipment (UE) 216 that is in the process of establishing an activetraffic channel connection with one or more Node Bs 204 is said to be ina connection setup state.

FIG. 3 is a block diagram illustrating a Node B 304 and a radio networkcontroller (RNC) 306 interfaced with a packet network interface 324.Only one Node B 304 is shown for simplicity. The Node B 304 and theradio network controller (RNC) 306 may be part of a radio networksubsystem (RNS) 308. The quantity of data to be transmitted by the NodeB 304 to a user equipment (UE) 116 may be retrieved from a data queue334 in the Node B 304 and provided to the channel element 332 fortransmission to the user equipment (UE) 116 associated with the dataqueue 334 via a radio frequency (RF) unit 336.

The radio network controller (RNC) 306 interfaces with a Public SwitchedTelephone Network (PSTN) 320 through a mobile switching center (MSC)322. Also, the radio network controller (RNC) 306 interfaces with a NodeB 304. In addition, the radio network controller (RNC) 306 may interfacewith a Packet Network Interface 324. The radio network controller (RNC)306 may coordinate the communication between a user equipment (UE) 116in the communication system and other users connected to the packetnetwork interface 324 and the public switched telephone network (PSTN)320. The public switched telephone network (PSTN) 320 may interface withusers through a standard telephone network (not shown).

The radio network controller (RNC) 306 may include many selectorelements 338. Each selector element 338 may be assigned to controlcommunication between one or more Node Bs 304 and one user equipment(UE) 116. If a selector element 338 has not been assigned to a givenuser equipment (UE) 116, a call control processor 340 may be informed ofthe need to page the user equipment (UE) 116. The call control processor340 may then direct the Node B 304 to page the user equipment (UE) 116.

The data source 326 may include a quantity of data that is to betransmitted to a given user equipment (UE) 116. The data source 326 mayprovide the data to a packet network interface 324. The packet networkinterface 324 receives the data and routes the data to the selectorelement 338. The selector element 338 then transmits the data to a NodeB 304 that is in communication with the target user equipment (UE) 116.Each Node B 304 may maintain a data queue 334 that stores the data to betransmitted to the user equipment (UE) 116.

For each data packet, the channel element 332 may insert the necessarycontrol fields. In one configuration, the channel element 332 mayperform a cyclic redundancy check (CRC) to encode the data packet andcontrol fields and insert a set of code tail bits. The data packet,control fields, CRC parity bits and code tail bits form a formattedpacket. In one configuration, the channel element 332 may then encodethe formatted packet and interleave (or reorder) the symbols within theencoded packet. The interleaved packet may be covered with a Walsh codeand spread with the short PNI and PNQ codes. The spread data is providedto a radio frequency (RF) unit 336 that quadrature modulates, filtersand amplifies the signal. The downlink signal is transmitted over theair through an antenna to the user equipment (UE) 116.

The Node B 304 may include a control unit 330 and memory 328. Thecontrol unit 330 may control each of the components of the Node B 304according to software stored in the memory 328.

FIG. 4 is a block diagram of a Node B 404 for use in the present systemsand methods. The Node B 404 of FIG. 4 may be one configuration of theNode Bs 104 illustrated in FIG. 1. In systems where multiple carriershave been deployed, energy management techniques may be introduced atthe Node B 404 based on the measured traffic in the system.

Potential solutions enabling energy savings within a UMTS Node B 404 mayexist. These solutions may consider the impacts on the time for legacyand new user equipments (UEs) 116 to gain access to service from a NodeB 404 and the impacts on legacy and new user equipments (UEs) 116 (e.g.,power consumption and mobility). Solutions that are backwards-compatibleand non-backwards-compatible may both be considered.

A Node B 404 may include two basic building blocks: a baseband unit(BBU) 442 and a radio equipment (RE) 456. The baseband unit (BBU) 442may also be referred to as a radio equipment control (REC). Both thebaseband unit (BBU) 442 and the radio equipment (RE) 456 may beco-located in a conventional radio base station design. The basebandunit (BBU) 442 may include the radio functions of the digital basebanddomain. The radio equipment (RE) 456 may include the analog radiofrequency functions.

A baseband unit (BBU) 442 may include subunits such as channel cards444, digital signal processors (DSPs) 446, field programmable gatearrays (FPGAs) 448, application specific integrated circuits (ASICs)450, clocks 452 and backhaul interface units 454. Portions of thesesubunits may be turned off to save power when they are not needed. Forexample, a baseband unit (BBU) 442 may include three channel cards 444.Depending on the load, two of the channel cards 444 may be shut off tosave power. Similarly, a subset of the E1s or T1s in the backhaulinterface units 454 may be shut off.

The radio equipment (RE) 456 may include a first downlink poweramplifier 458 a coupled to a first antenna 460 a. If the Node B 404 isused for multiple-input and multiple-output (MIMO) transmissions, theradio equipment (RE) 456 may also include a second downlink poweramplifier 458 b coupled to a second antenna 460 b. In one configuration,a radio equipment (RE) 456 may include more than two downlink poweramplifiers 458. For example, a Node B 404 may be using multiple carriers(non-MIMO) across multiple power amplifiers 458. The Node B 404 may shutoff one or more downlink power amplifiers 458 to reduce the powerconsumption of the Node B 404. If the Node B 404 shuts off a carrier,the Node B 404 may shut off the downlink power amplifiers 458 associatedwith the carrier.

Reduction in energy consumption may be accomplished by determining theenergy consumption breakdown in existing Node Bs 404, establishing NodeB 404 energy saving targets and identifying solutions based on theexisting Uu interface 101 that rely on Node B 404 implementationenhancements as well as UTRAN operation. If the targets are still notmet, solutions may be identified that can help achieve the targets byway of modifications to 3GPP specifications. Each solution may need tobe characterized based on the impact to the system.

The Node B 404 may include an energy management module 462. The Node B404 may use the energy management module 462 to determine when to makeadjustments that may reduce the energy consumption of the Node B 404.The energy management module 462 may include a carrier load threshold464. The carrier load threshold 464 may be a preset threshold thatdefines the minimum carrier load when the Node B 404 shuts off one ormore carriers or one or more subunits of the baseband unit (BBU) 442 toreduce the power consumption of the Node B 404. The energy managementmodule 462 may also include a combined carrier load threshold 466. Ifthe Node B 404 has shut off one or more carriers to conserve energy, thecombined carrier load threshold 466 may be a preset maximum load on thecarriers that are turned on before the Node B 404 turns a shut offcarrier back on. The carrier load threshold 464 is discussed inadditional detail below in relation to FIG. 6 and FIG. 7. The combinedcarrier load threshold 466 is discussed in additional detail below inrelation to FIG. 6 and FIG. 7.

FIG. 5 is a block diagram of a Node B 504 with multiple radio equipments(RE) 556 a-b that are separated from the radio equipment control (REC)542. The radio equipment control (REC) 542 may be a Baseband Unit (BBU)442. Each radio equipment (RE) 556 may be close to an antenna while theradio equipment control (REC) 542 is located in a convenientlyaccessible site. For the UMTS radio access network (RAN) 118, the radioequipment control (REC) 542 provides access to a radio networkcontroller (RNC) 106 via the Iub interface 114, whereas the radioequipment (RE) 556 serves as the air interface, called the Uu interface101, to the user equipment (UE) 116. Table 1 lists the functionsperformed both on the uplink and the downlink by the radio equipmentcontrol (REC) 542 and the radio equipment (RE) 556.

TABLE 1 Functions of REC or BBU Functions of RE Downlink Uplink DownlinkUplink Radio base station control & management Iub transport RRC ChannelFiltering Iub Frame protocols D/A conversion A/D conversion ChannelCoding Channel De-coding Up Conversion Down Conversion InterleavingDe-Interleaving ON/OFF control of Automatic Gain each carrier ControlSpreading De-spreading Carrier Multiplexing Carrier De- multiplexingScrambling De-scrambling Power amplification Low Noise MIMO processingand limiting Amplification Adding of physical Signal distribution toAntenna supervision channels signal processing units Transmit PowerTransmit Power RF filtering RF filtering Control of each Control &Feedback physical channel Information detection Frame and slot signalgeneration (including clock stabilization) Reference FrequencyGeneration Measurements Measurements

FIG. 6 is a flow diagram of a method 600 for reducing power consumptionof a Node B 404 by switching off multiple-input and multiple-output(MIMO) transmissions. The method 600 may be performed by a Node B 404.In one configuration, the method 600 may be performed by a radio networkcontroller (RNC) 106 via instructions sent to a Node B 404. The Node B404 may transmit 602 a first pilot channel via a first antenna 460 ausing a first downlink power amplifier 458 a and a second pilot channelvia a second antenna 460 b using a second downlink power amplifier 458b. The pilot channels may be used for multiple-input and multiple-output(MIMO) transmissions to one or more user equipments (UEs) 116 that arein communication with the Node B 404.

The Node B 404 may determine 604 whether there are any multiple-inputand multiple-output (MIMO) users in the cell. A multiple-input andmultiple-output (MIMO) user may refer to a user equipment (UE) 116 thatis within the boundaries covered by a Node B 404 that iscapable/configured for multiple-input and multiple-output (MIMO)communications. If there are multiple-input and multiple-output (MIMO)users in the cell, the Node B 404 may continue transmitting 602 both thefirst pilot channel via the first antenna 460 a using the first downlinkpower amplifier 458 a and the second pilot channel via the secondantenna 460 b using the second downlink power amplifier 458 b.

If there are no multiple-input and multiple-output (MIMO) users in thecell, the Node B 404 may shut off 606 the second pilot channel and thesecond downlink power amplifier 458 b. This may lead to significantenergy savings. The Node B 404 may thus reduce the power consumption ofthe Node B 404 by eliminating the power used by the second poweramplifier 458 b to transmit the second pilot channel during times whenthe second pilot channel is not needed. The Node B 404 may transmit 608only the first pilot channel via the first antenna 460 a using the firstdownlink power amplifier 458 a. The Node B 404 may then again determine604 whether there are any multiple-input and multiple-output (MIMO)users in the cell.

FIG. 7 is a flow diagram of a method 700 for reducing power consumptionof a Node B 404 by shutting off one or more carriers. The method 700 maybe performed by a Node B 404. In one configuration, the method 700 maybe performed by a radio network controller (RNC) 106 via instructionssent to a Node B 404. The Node B 404 may communicate 704 with one ormore user equipments (UEs) 116 using n carriers.

The Node B 404 may determine 706 whether the load of any of the ncarriers is below a carrier load threshold 464. The carrier loadthreshold 464 may be a preset threshold that defines the minimum numberof user equipments (UEs) 116 utilizing a carrier before the Node B 404redirects the user equipments (UEs) 116 to another carrier and shuts offthe carrier. A user equipment (UE) 116 may be either a single-carrieruser equipment (UE) 116 or a user equipment (UE) 116 that is capable ofcommunicating with a Node B 404 using multiple carriers.

If the load of none of the n carriers is below the carrier loadthreshold 464, the Node B 404 may continue communicating 704 with theone or more user equipments (UEs) 116 using the n carriers. If the loadof any of the carriers is below the carrier load threshold 464, the NodeB 404 may redirect 708 one or more user equipments (UEs) 116 from theone or more carriers with loads below the carrier load threshold 464 tothe one or more carriers with loads above the carrier load threshold 464(this may apply until only one carrier remains). In one configuration,the Node B 404 may redirect 708 the one or more user equipments (UEs)116 from the one or more carriers with loads below the carrier loadthreshold 464 to one or more carriers with loads that are currentlybelow the carrier load threshold 464 (but that will have loads above thecarrier load threshold 464 once the user equipments (UEs) 116 areredirected to them). Redirecting 708 the one or more user equipments(UEs) 116 from a carrier with a load below the carrier load threshold464 to one or more carriers with loads above the carrier load threshold464 may include instructing the one or more user equipments (UEs) 116 toswitch to a different modulation and coding scheme and a differentfrequency. In one configuration, the Node B 404 may redirect the one ormore user equipments (UEs) 116 to multiple carriers (i.e., not all theuser equipments (UEs) 116 will go to the same carrier). In anotherconfiguration, the Node B 404 may reduce the amount of carriers that auser equipment (UE) 116 is configured for (i.e., if there is a smallnumber of user equipments (UEs) 116 that can communicate using threedifferent carriers and not enough data demand (from the mix of userequipment (UE) 116 types and quantity), the Node B 404 may reconfigurethose multi-carrier user equipments (UEs) 116 to use only one or twocarriers and shut off the extra carrier(s)).

The Node B 404 may then turn off 710 the one or more carriers with loadsbelow the carrier load threshold and the physical equipmentcorresponding to the one or more carriers. By turning off one or morecarriers during periods where the load is minimal, all or parts of thebaseband unit (BBU) 442 and radio equipment (RE) 456 may be turned off,leading to a potentially large reduction in energy consumption at theNode B 404. The Node B 404 may communicate 712 with the one or more userequipments (UEs) 116 using the one or more carriers with loads above thecarrier load threshold 464.

The Node B 404 may determine 713 whether the load of any of the one ormore carriers is below the carrier load threshold 464. If the load ofany of the one or more carriers is below the carrier load threshold 464,the Node B 404 may redirect 708 the one or more user equipments (UEs)116 from the one or more carriers with loads below the carrier loadthreshold 464 to the one or more carriers with loads above the carrierload threshold 464. If the load of none of the n carriers is below thecarrier load threshold 464, the Node B 404 may determine 714 whether thetotal load of the one or more carriers with loads above the carrier loadthreshold 464 is above a combined carrier threshold 466. The combinedcarrier threshold 466 may be a threshold used by the Node B 404 todetermine when to resume communications using a previous-switched-offcarrier after the previously-switched-off carrier has been turned off toreduce energy consumption.

If the total load of the one or more carriers is not above the combinedcarrier threshold 466, the Node B 404 may continue communicating 712with the one or more user equipments (UEs) 116 using the one or morecarriers with loads above the carrier load threshold 464. If the totalload of the one or more carriers is above the combined carrier threshold466, the Node B 404 may turn on 716 a previously-switched-off carrierand the physical equipment corresponding to the previously-switched-offcarrier. The Node B 404 may next redirect 718 one or more userequipments (UEs) 116 from the one or more carriers with loads above thecarrier load threshold 464 to the previously-switched-off carrier. TheNode B 404 may then communicate 712 with the one or more user equipments(UEs) 116 using the one or more carriers with loads above the carrierload threshold 464.

FIG. 8 is a flow diagram of a method 800 for disabling baseband unit(BBU) 442 subunits to reduce energy consumption on a Node B 404. Themethod 800 may be performed by a Node B 404. In one configuration, themethod 800 may be performed by a radio network controller (RNC) 106 viacommands to the Node B 404. The Node B 404 may communicate 802 with oneor more user equipments (UEs) 116 using one or more carriers and allbaseband unit (BBU) 442 subunits for each of the one or more carriers.The Node B 404 may determine 804 whether the load of any of the one ormore carriers is below a carrier load threshold 464. If the load of anyof the one or more carriers is not below a carrier load threshold 464,the Node B 404 may continue communicating 802 with the one or more userequipments (UEs) 116 using the one or more carriers and all the basebandunit (BBU) 442 subunits for each of the one or more carriers.

If the load of any of the one or more carriers is below a carrier loadthreshold 464, the Node B 404 may determine 806 one or more basebandunit (BBU) 442 subunits to disable on the one or more carriers. Forexample, the Node B 404 may determine to disable channel cards 444,digital signal processors (DSPs) 446, field programmable gate arrays(FPGAs) 448, application-specific integrated circuits (ASICs) 450 orclocks 452 as a function of the load. The Node B 404 may also determineto disable backhaul interface units 454. In one configuration, the NodeB 404 may determine 806 to disable the same baseband unit (BBU) 442subunit for each of the one or more carriers. In another configuration,the Node B 404 may determine 806 different baseband unit (BBU) 442subunits to disable for each carrier of the one or more carriers. TheNode B 404 may then disable 808 the determined one or more baseband unit(BBU) 442 subunits. The Node B 404 may next communicate 810 with the oneor more user equipments (UEs) 116 using the one or more carriers andonly the baseband unit (BBU) 442 subunits that have not been disabled.In one configuration, the Node B 404 may use multiple carrier loadthresholds 464 to iteratively shut off baseband unit (BBU) 442 subunits.

The Node B 404 may determine 812 whether the load of any of the one ormore carriers with all baseband unit (BBU) 442 subunits enabled is belowthe carrier load threshold 464. If the load of any of the one or morecarriers with all baseband unit (BBU) 442 subunits enabled is below thecarrier load threshold 464, the Node B 404 may determine 806 one or morebaseband unit (BBU) 442 subunits to disable on the one or more carriers.If none of the one or more carriers with all baseband unit (BBU) 442subunits enabled has a load below the carrier load threshold 464, theNode B 404 may determine 813 whether the total load of the one or morecarriers is above a combined carrier load threshold 466. If the totalload of the one or more carriers is not above the combined carrier loadthreshold 466, the Node B 404 may continue communicating 810 with theone or more user equipments (UEs) 116 using the one or more carriers andonly the baseband unit (BBU) 442 subunits that have not been disabled.If the total load of the one or more carriers is above the combinedcarrier load threshold 466, the Node B 404 may re-enable 814 some or allof the disabled baseband unit (BBU) 442 subunits. The Node B 404 maythen return to communicating 810 with the one or more user equipments(UEs) 116 using the one or more carriers and only the baseband unit(BBU) 442 subunits that have not been disabled.

FIG. 9 is a block diagram of a transmitter structure and/or processimplemented in a Node B 404. The functions and components shown in FIG.9 may be implemented by software, hardware or a combination of softwareand hardware. Other functions may be added to FIG. 9 in addition to orinstead of the functions shown in FIG. 9.

A data source 968 may provide data d(t) 970 to a frame quality indicator(FQI)/encoder 972. The frame quality indicator (FQI)/encoder 972 mayappend a frame quality indicator (FQI) such as cyclic redundancy check(CRC) to the data d(t) 970. The frame quality indicator (FQI)/encoder972 may further encode the data d(t) 970 using one or more codingschemes to provide encoded symbols 974. Each coding scheme may includeone or more types of coding, e.g., convolutional coding, Turbo coding,block coding, repetition coding, other types of coding or no coding atall. Other coding schemes may include automatic repeat request (ARQ),hybrid ARQ (H-ARQ) and incremental redundancy repeat techniques.Different types of data may be encoded with different coding schemes.

An interleaver 976 may interleave the encoded data symbols 974 in timeto combat fading. The interleaver 976 may output interleaved symbols978. The interleaved symbols 978 may be mapped by a frame formatter 980to a pre-defined frame format to produce a frame 982. In oneconfiguration, a frame format may specify the frame as being composed ofa plurality of sub-segments. In another configuration, sub-segments maybe any successive portions of a frame 982 along a given dimension, e.g.,time, frequency, code or any other dimension. A frame 982 may becomposed of a fixed plurality of such sub-segments, each sub-segmentcontaining a portion of the total number of symbols allocated to theframe. For example, in a wireless communication system that isconfigured according to the W-CDMA standard, a sub-segment may bedefined as a slot. The interleaved symbols 978 may be segmented into aplurality S of sub-segments making up a frame 982.

A frame formatter 980 may further specify the inclusion of controlsymbols (not shown) along with the interleaved symbols 978. Such controlsymbols may include power control symbols, frame format informationsymbols, etc.

A modulator 984 may modulate the frame 982 to generate modulated data986. Examples of modulation techniques include binary phase shift keying(BPSK) and quadrature phase shift keying (QPSK). The modulator 984 mayalso repeat a sequence of modulated data 986.

A baseband-to-radio-frequency (RF) conversion block 988 may convert themodulated data 986 to a radio frequency (RF) signal 990 for transmissionvia an antenna 960 over a wireless communication link to one or moreuser equipments (UEs) 116.

FIG. 10 illustrates certain components that may be included within aNode B 1004. A Node B 1004 may also be referred to as, and may includesome or all of the functionality of, an access point, a broadcasttransmitter, a base station, an evolved NodeB, etc. The Node B 1004includes a processor 1003. The processor 1003 may be a general purposesingle- or multi-chip microprocessor (e.g., an ARM), a special purposemicroprocessor (e.g., a digital signal processor (DSP)), amicrocontroller, a programmable gate array, etc. The processor 1003 maybe referred to as a central processing unit (CPU). Although just asingle processor 1003 is shown in the Node B 1004 of FIG. 10, in analternative configuration, a combination of processors (e.g., an ARM andDSP) could be used.

The Node B 1004 also includes memory 1005. The memory 1005 may be anyelectronic component capable of storing electronic information. Thememory 1005 may be embodied as random access memory (RAM), read onlymemory (ROM), magnetic disk storage media, optical storage media, flashmemory devices in RAM, on-board memory included with the processor,EPROM memory, EEPROM memory, registers, and so forth, includingcombinations thereof.

Data 1007 a and instructions 1009 a may be stored in the memory 1005.The instructions 1009 a may be executable by the processor 1003 toimplement the methods disclosed herein. Executing the instructions 1009a may involve the use of the data 1007 a that is stored in the memory1005. When the processor 1003 executes the instructions 1009 a, variousportions of the instructions 1009 b may be loaded onto the processor1003, and various pieces of data 1007 b may be loaded onto the processor1003.

The Node B 1004 may also include a transmitter 1011 and a receiver 1013to allow transmission and reception of signals to and from the Node B1004. The transmitter 1011 and receiver 1013 may be collectivelyreferred to as a transceiver 1015. Multiple antennas 1017 a-b may beelectrically coupled to the transceiver 1015. The Node B 1004 may alsoinclude (not shown) multiple transmitters, multiple receivers, multipletransceivers and/or additional antennas.

The Node B 1004 may include a digital signal processor (DSP) 1021. TheNode B 1004 may also include a communications interface 1023. Thecommunications interface 1023 may allow a user to interact with the NodeB 1004.

The various components of the Node B 1004 may be coupled together by oneor more buses, which may include a power bus, a control signal bus, astatus signal bus, a data bus, etc. For simplicity, the various busesare illustrated in FIG. 10 as a bus system 1019.

FIG. 11 illustrates certain components that may be included within aradio network controller (RNC) 1175. A radio network controller (RNC)1175 is a governing element in the UMTS radio access network (UTRAN)that is responsible for controlling the Node Bs 1004 that are connectedto it. The radio network controller (RNC) 1175 may be connected to acircuit switched core network through a media gateway. The radio networkcontroller (RNC) 1175 includes a processor 1103. The processor 1103 maybe a general purpose single- or multi-chip microprocessor (e.g., anARM), a special purpose microprocessor (e.g., a digital signal processor(DSP)), a microcontroller, a programmable gate array, etc. The processor1103 may be referred to as a central processing unit (CPU). Althoughjust a single processor 1103 is shown in the radio network controller(RNC) 1175 of FIG. 11, in an alternative configuration, a combination ofprocessors (e.g., an ARM and DSP) could be used.

The radio network controller (RNC) 1175 also includes memory 1105. Thememory 1105 may be any electronic component capable of storingelectronic information. The memory 1105 may be embodied as random accessmemory (RAM), read only memory (ROM), magnetic disk storage media,optical storage media, flash memory devices in RAM, on-board memoryincluded with the processor, EPROM memory, EEPROM memory, registers, andso forth, including combinations thereof.

Data 1107 a and instructions 1109 a may be stored in the memory 1105.The instructions 1109 a may be executable by the processor 1103 toimplement the methods disclosed herein. Executing the instructions 1109a may involve the use of the data 1107 a that is stored in the memory1105. When the processor 1103 executes the instructions 1109 a, variousportions of the instructions 1109 b may be loaded onto the processor1103, and various pieces of data 1107 b may be loaded onto the processor1103.

The radio network controller (RNC) 1175 may include a digital signalprocessor (DSP) 1121. The various components of the radio networkcontroller (RNC) 1175 may be coupled together by one or more buses,which may include a power bus, a control signal bus, a status signalbus, a data bus, etc. For the sake of simplicity, the various buses areillustrated in FIG. 11 as a bus system 1119.

The techniques described herein may be used for various communicationsystems, including communication systems that are based on an orthogonalmultiplexing scheme. Examples of such communication systems includeOrthogonal Frequency Division Multiple Access (OFDMA) systems,Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems, andso forth. An OFDMA system utilizes orthogonal frequency divisionmultiplexing (OFDM), which is a modulation technique that partitions theoverall system bandwidth into multiple orthogonal sub-carriers. Thesesub-carriers may also be called tones, bins, etc. With OFDM, eachsub-carrier may be independently modulated with data. An SC-FDMA systemmay utilize interleaved FDMA (IFDMA) to transmit on sub-carriers thatare distributed across the system bandwidth, localized FDMA (LFDMA) totransmit on a block of adjacent sub-carriers, or enhanced FDMA (EFDMA)to transmit on multiple blocks of adjacent sub-carriers. In general,modulation symbols are sent in the frequency domain with OFDM and in thetime domain with SC-FDMA.

The term “determining” encompasses a wide variety of actions and,therefore, “determining” can include calculating, computing, processing,deriving, investigating, looking up (e.g., looking up in a table, adatabase or another data structure), ascertaining and the like. Also,“determining” can include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” can include resolving, selecting, choosing, establishingand the like.

The phrase “based on” does not mean “based only on,” unless expresslyspecified otherwise. In other words, the phrase “based on” describesboth “based only on” and “based at least on.”

The term “processor” should be interpreted broadly to encompass ageneral purpose processor, a central processing unit (CPU), amicroprocessor, a digital signal processor (DSP), a controller, amicrocontroller, a state machine, and so forth. Under somecircumstances, a “processor” may refer to an application specificintegrated circuit (ASIC), a programmable logic device (PLD), a fieldprogrammable gate array (FPGA), etc. The term “processor” may refer to acombination of processing devices, e.g., a combination of a DSP and amicroprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The term “memory” should be interpreted broadly to encompass anyelectronic component capable of storing electronic information. The termmemory may refer to various types of processor-readable media such asrandom access memory (RAM), read-only memory (ROM), non-volatile randomaccess memory (NVRAM), programmable read-only memory (PROM), erasableprogrammable read-only memory (EPROM), electrically erasable PROM(EEPROM), flash memory, magnetic or optical data storage, registers,etc. Memory is said to be in electronic communication with a processorif the processor can read information from and/or write information tothe memory. Memory that is integral to a processor is in electroniccommunication with the processor.

The terms “instructions” and “code” should be interpreted broadly toinclude any type of computer-readable statement(s). For example, theterms “instructions” and “code” may refer to one or more programs,routines, sub-routines, functions, procedures, etc. “Instructions” and“code” may comprise a single computer-readable statement or manycomputer-readable statements.

The functions described herein may be implemented in software orfirmware being executed by hardware. The functions may be stored as oneor more instructions on a computer-readable medium. The terms“computer-readable medium” or “computer-program product” refers to anytangible storage medium that can be accessed by a computer or aprocessor. By way of example, and not limitation, a computer-readablemedium may comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray® disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isrequired for proper operation of the method that is being described, theorder and/or use of specific steps and/or actions may be modifiedwithout departing from the scope of the claims.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein, suchas those illustrated by FIGS. 6, 7 and 8, can be downloaded and/orotherwise obtained by a device. For example, a device may be coupled toa server to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via a storage means (e.g., random access memory (RAM),read-only memory (ROM), a physical storage medium such as a compact disc(CD) or floppy disk, etc.), such that a device may obtain the variousmethods upon coupling or providing the storage means to the device.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the systems, methods, and apparatus described herein withoutdeparting from the scope of the claims.

What is claimed is:
 1. A method for reducing energy consumption of abase station, comprising: transmitting a first pilot channel via a firstantenna using a first downlink power amplifier; transmitting a secondpilot channel via a second antenna using a second downlink poweramplifier; determining that no multiple-input and multiple-output usersare in a cell corresponding to the base station; and shutting off thesecond pilot channel.
 2. The method of claim 1, wherein shutting off thesecond pilot channel comprises shutting off the second downlink poweramplifier.
 3. The method of claim 1, wherein the base station is a NodeB.
 4. The method of claim 1, wherein the method is performed by a radionetwork controller via instructions sent to the base station.
 5. Themethod of claim 1, wherein the first pilot channel and the second pilotchannel are used for multiple-input and multiple-output transmissions toa user equipment.
 6. A wireless device configured for reducing energyconsumption, comprising: a processor; memory in electronic communicationwith the processor; instructions stored in the memory, the instructionsbeing executable by the processor to: transmit a first pilot channel viaa first antenna using a first downlink power amplifier; transmit asecond pilot channel via a second antenna using a second downlink poweramplifier; determine that no multiple-input and multiple-output usersare in a cell corresponding to the wireless device; and shut off thesecond pilot channel.
 7. The wireless device of claim 6, wherein theinstructions executable by the processor to shut off the second pilotchannel comprise instructions executable by the processor to shut offthe second downlink power amplifier.
 8. The wireless device of claim 6,wherein the wireless device is a Node B.
 9. The wireless device of claim6, wherein the wireless device receives instructions from a radionetwork controller.
 10. The wireless device of claim 6, wherein thefirst pilot channel and the second pilot channel are used formultiple-input and multiple-output transmissions to a user equipment.11. A wireless device configured for reducing energy consumption,comprising: means for transmitting a first pilot channel via a firstantenna using a first downlink power amplifier; means for transmitting asecond pilot channel via a second antenna using a second downlink poweramplifier; means for determining that no multiple-input andmultiple-output users are in a cell corresponding to the wirelessdevice; and means for shutting off the second pilot channel.
 12. Thewireless device of claim 11, wherein the means for shutting off thesecond pilot channel comprise means for shutting off the second downlinkpower amplifier.
 13. A computer-program product for reducing energyconsumption of a base station, the computer-program product comprising anon-transitory computer-readable medium having instructions thereon, theinstructions comprising: code for causing a base station to transmit afirst pilot channel via a first antenna using a first downlink poweramplifier; code for causing the base station to transmit a second pilotchannel via a second antenna using a second downlink power amplifier;code for causing the base station to determine that no multiple-inputand multiple-output users are in a cell corresponding to the basestation; and code for causing the base station to shut off the secondpilot channel.
 14. The computer-program product of claim 13, wherein thecode for causing the base station to shut off the second pilot channelcomprises code for causing the base station to shut off the seconddownlink power amplifier.